Comcast has added Michigan to its list of states - including Pennsylvania, California, Colorado, Illinois and Florida -- where the cable ISP is offering services that support the next-generation Internet standard known as IPv6.

A leader in IPv6 deployment, Comcast has thousands of customers in the United States that are participating in its ongoing trial of IPv6 services. Comcast began its IPv6 trial 16 months ago to test several different transition mechanisms between IPv4, the Internet's current addressing scheme, and IPv6.

IPv6 features an expanded addressing scheme that can support billions of devices connected directly to the Internet at faster speeds and lower cost than IPv4, which is running out of address space.

"At this point, everything is going very well with our trials," says John Brzozowski, distinguished engineer and chief architect for IPv6 at Comcast. "We're into a production deployment planning phase at this point."

Brzozowski says Comcast's cable modem customers are having a good experience with IPv6-based services over its DOCSIS network. DOCSIS -- which stands for Data Service Over Cable Service Interface Specification -- is the standard for sending high-speed data over cable television networks.

"DOCSIS technology is in a good place as far as supporting IPv6 is concerned," Brzozowski says. "We didn't see anything adverse during the trials...We're really positioned well in terms of enabling IPv6 support for our subscribers."

"Given the success we're seeing...we're going to keep expanding the availability of IPv6 and keep marching towards a production launch," Brzozowski says. "We're getting to the place where we can turn it on and leave it on."

Comcast said it is getting more inquiries from customers about IPv6 services since June 8, when a large-scale trial of the emerging standard was held. World IPv6 Day was such a success that it prompted some Web site operators including Google and Facebook to permanently support IPv6 on some of their public-facing Web sites.

"The dwindling of address space for IPv4 and the press around World IPv6 Day has prompted a lot of inquiries," Brzozowski says. "We've seen a great deal of interest from people from all walks of life. Initially, it was all residential, but now we're getting inquiries from commercial users."

Carriers like Comcast are migrating to IPv6 because the Internet is running out of addresses using IPv4. The free pool of unassigned IPv4 addresses expired in February, and in April the Asia Pacific region ran out of all but a few IPv4 addresses being held in reserve for startups. The American Registry for Internet Numbers (ARIN), which doles out IP addresses to network operators in North America, says it will deplete its supply of IPv4 addresses this fall.

IPv4 uses 32-bit addresses and can support 4.3 billion devices connected directly to the Internet, but IPv6 uses 128-bit addresses and can connect up a virtually unlimited number of devices: 2 to the 128th power. IPv6 offers the promise of faster, less-costly Internet services than the alternative, which is to extend the life of IPv4 using network address translation (NAT) devices.